For actual multi-channel differential signaling system, the ideal balance or symmetrical topology cannot be established, and hence, an imbalance component is excited. However a theoretical analysis method of evaluating the voltage and current distribution on the differential-paired lines, which allows to anticipate EM radiation at the design stage and to study possible means for suppressing imbalance components, has not been implemented. To provide the basic considerations for electromagnetic (EM) radiation from practical asymmetrical differential-paired lines structure with equi-length routing used in high-speed board design, this paper newly proposes an analytical method for evaluating the voltage and current at any point on differential-paired lines by expressing the differential paired-lines with an equivalent source circuit and an equivalent load circuit. The proposed method can predict S-parameters, distributions of voltage and current and EM radiation with sufficient accuracy. In addition, the proposed method provides enough flexibility for different geometric parameters and can be used to develop physical insights and design guidelines. This study has successfully established a basic method to effectively predict signal integrity and EM interference issues on a differential-paired lines.

To provide basic considerations for the realization of method for suppressing the EMI from differential-paired lines on flexible printed circuits (FPC), the characteristics of the SI performance and shielding effectiveness (SE) of shielded-flexible printed circuits for differential-signaling are investigated in this paper experimentally and by a numerical modeling. Firstly, transmission characteristics of TDR measurement and frequency response of |Sdd21| are discussed, from view point of signal integrity. Secondly, as the characteristics of the SE performance for EMI, frequency responses of magnetic field are investigated. Although placement of conductive shield near the paired-lines decreases characteristics impedance, |Sdd21| for the “with Cu 5.5 µm-thickness copper shield” is not deteriorated compared with “without shield” and sufficient SE performance for magnetic field can be established. But, thin-shield deteriorates SI as well as SE performances. The frequency response of |Sdd21| at higher frequencies for the “Ag 0.1 µm” case has the steep loss roll off. A reflection loss resulted from impedance-mismatching is not dominant factor of the losses. The dominant factor may be magnetic field leakage due to very thin-conductive shield.

A connector model expressed as an inductance is proposed for use in a previously reported common-mode antenna model. The common-mode antenna model is an equivalent model for estimating only common-mode radiation from a printed circuit board (PCB) more quickly and with less computational resources than a calculation method that fully divides the entire structure of the PCB into elemental cells, such as narrow signal traces and thin dielectric layers. Although the common-mode antenna model can estimate the amount of radiation on the basis of the pin configuration of the connector between two PCBs, the calculation results do not show the peak frequency shift in the radiation spectrum when there is a change in the pin configuration. A previous study suggested that the frequency shift depends on the total inductance of the connector, which led to the development of the connector model reported here, which takes into account the effective inductance of the connector. The common-mode antenna model with the developed connector model accurately simulates the peak frequency shift caused by a change in the connector pin configuration. The results agree well with measured spectra (error of 3 dB).

A novel high common-mode (CM) suppression wideband balanced passband filter (BPF) is proposed using the stub centrally loaded slotline resonators (SCLSR) which have two resonant frequencies (odd- and even-modes) in the desired passband. The odd-mode resonant frequency of the slotline SCLSR can be flexibly controlled by the stub, whereas the even-mode one is fixed. Meanwhile, a transmission zero near the odd-mode resonant frequency can be generated due to the main path signal counteraction. First, the wideband single-ended BPF and corresponding balanced BPF are designed based on the slotline SCLSR with the parallel coupled microstrip line input/output (I/O). Ultra wideband high CM suppression that can be achieved for the slotline resonator structure has no resonant mode under CM excitation. Furthermore, by folding the parallel coupled microstrip line I/O, the source-load coupling is effectively decoupled to improve the CM suppression within the passband. The high suppression wideband balanced BPF is fabricated and measured, respectively. Good agreement between simulation and measurement results is obtained.

An imbalance difference model has been developed to estimate the common-mode radiated emission of a PCB with an attached cable. This model, however, requires significant computation time for full-wave simulation, especially if the attached cable is long, even with a powerful computer configuration. To solve this problem, a method that approximates the imbalance difference model as an equivalent asymmetrical dipole antenna is proposed in this paper. The common-mode radiated emission can be predicted using a line integration of the common-mode current distribution which is directly estimated by the asymmetrical antenna model. Unlike existing methods, the proposed method avoids the circuit construction normally used to measure the common-mode current, and is still able to accurately predict the maximum common-mode radiation. The effectiveness of the proposed method is verified by comparing the predicted results with the 3D full-wave simulation and the measured data gathered in an anechoic chamber.

This paper proposes an ultra-low-voltage, wide signal swing, and clock-scalable differential dynamic amplifier using a common-mode voltage detection technique. The essential characteristics of an amplifier, such as gain, linearity, power consumption, noise, etc., are analyzed. In measurement, the proposed dynamic amplifier achieves a 13dB gain with less than 1dB drop over a differential output signal swing of 340mVpp with a supply voltage of 0.5V. The attained maximum operating frequency is 700MHz. With a 0.7V supply, the gain increases to 16dB with a signal swing of 700mVpp. The prototype amplifier is fabricated in 90nm CMOS technology with the low threshold voltage and the deep N-well options.

This paper presents a possibility of Electromagnetic (EM) analysis against cryptographic modules outside their security boundaries. The mechanism behind the information leakage is explained from the view point of Electromagnetic Compatibility: electric fluctuation released from cryptographic modules can conduct to peripheral circuits based on ground bounce, resulting in radiation. We demonstrate the consequence of the mechanism through experiments where the ISO/IEC standard block cipher AES (Advanced Encryption Standard) is implemented on an FPGA board and EM radiations from power and communication cables are measured. Correlation Electromagnetic Analysis (CEMA) is conducted in order to evaluate the information leakage. The experimental results show that secret keys are revealed even though there are various disturbing factors such as voltage regulators and AC/DC converters between the target module and the measurement points. We also discuss information-suppression techniques as electrical-level countermeasures against such CEMAs.

This paper demonstrates a FinFET operational amplifier (opamp), which is suitable to be integrated with digital circuits in a scaled low-standby-power (LSTP) technology and operates at extremely low voltage. The opamp is consisting of an adaptive threshold-voltage (Vt) differential pair and a low-voltage source follower using independent-double-gate- (IDG-) FinFETs. These two components enable the opamp to extend the common-mode voltage range (CMR) below the nominal Vt even if the supply voltage is less than 1.0 V. The opamp was implemented by our FinFET technology co-integrating common-DG- (CDG-) and IDG-FinFETs. More than 40-dB DC gain and 1-MHz gain-bandwidth product in the 500-mV-wide input CMR at the supply voltage of 0.7 V was estimated with SPICE simulation. The fabricated chip successfully demonstrated the 0.7-V operation with the 480-mV-wide CMR, even though the nominal Vt was 400 mV.

When contact failure occurs in a connector in a coaxial high-frequency (HF) signal transmission line, it is well known that common-mode (CM) radiation occurs on the line. We focus on contact conditions in a connector causing such CM radiation. Experiments and simulations verify that CM radiation increases as the contact resistance increases. While the CM current strongly depends on the distribution pattern of contact resistances at a low resistance, the CM current does not depend on these pattern at a high resistance. Our results indicate that it is important to maintain a symmetrical distribution of contact spots whenever the number of such spots is four or more.

Recently, for electronic devices operating at high frequencies, the suppression of a high-frequency electromagnetic field of 1 GHz or more has become necessary. We focus on a loose connector between a pair of electrical devices operating in the high-frequency band. Many electronic devices are used in living spaces, most of which are connected to one another. When a user connects two devices, achieving good contact only by finger tightening can be difficult. Accordingly, in this paper, considering the case where the tightening torque of a coaxial connector is insufficient, we analyze the effect of loose contact on electromagnetic field radiation from a transmission line.

This paper presents the new switching converter model used for analyzing the generation mechanism of ringing ground leakage (GL) current, generated during the transient, at switch on/off of any switching converter. By applying the Norton model, the proposed new model of switching converter can be formulated. The ringing GL current is evaluated at the switching on/off of the unbalanced (half-bridge converter) and the balanced converter (full-bridge converter) for bidirectional D.C. motor drive used as an example. It is concluded that the measured and simulated results of the generated GL current agree well with the numerical analysis results, analyzed by the proposed new model of switching converter, in terms of the minimum or maximum peak currents and the ringing frequency.

In this paper, we studied the use of common-mode noise reduction technique for in-vehicle electronic equipment in an actual instrument design. We have improved the circuit model of the common-mode noise that flows to the wire harness to add the effect of a bypass capacitor located near the LSI. We analyzed the improved circuit model using a circuit simulator and verified the effectiveness of the noise reduction condition derived from the circuit model. It was also confirmed that offsetting the impedance mismatch in the PCB section requires to make a circuit constant larger than that necessary for doing the impedance mismatch in the LSI section. An evaluation circuit board comprising an automotive microcomputer was prototyped to experiment on the common-mode noise reduction effect of the board. The experimental results showed the noise reduction effect of the board. The experimental results also revealed that the degree of impedance mismatch in the LSI section can be estimated by using a PCB having a known impedance. We further inquired into the optimization of impedance parameters, which is difficult for actual products at present. To satisfy the noise reduction condition composed of numerous parameters, we proposed a design method using an optimization algorithm and an electromagnetic field simulator, and confirmed its effectiveness.

In a differential transmission line, a large common-mode radiation is excited due to its asymmetry. In this paper, the imbalance difference model, which was proposed by the authors for estimation of common-mode radiation, is extended to apply to the differential signaling systems. The authors focus on a differential transmission line with asymmetric property, which consists of an adjacent return plane and two signal lines which are placed close to an edge of the return plane. Three orthogonal transmission modes, a normal mode, a primary common mode and a secondary common mode, are defined. Among these transmission modes, the secondary common mode is dominant in radiation, and a mechanism of the secondary common-mode generation is explained. The radiated emission which was calculated using the imbalance difference model was in good agreement with that obtained by full wave calculation.

In this paper, we propose an optimization system with parallel processing for reducing electromagnetic interference (EMI) on electronic control unit (ECU). We adopt simulated annealing (SA), genetic algorithm (GA) and taboo search (TS) to seek optimal solutions, and a Spice-like circuit simulator to analyze common-mode current. Therefore, the proposed system can determine the adequate combinations of the parasitic inductance and capacitance values on printed circuit board (PCB) efficiently and practically, to reduce EMI caused by the common-mode current. Finally, we apply the proposed system to an example circuit to verify the validity and efficiency of the system.

A 0.9-V 12-bit 40-MSPS pipeline ADC with I/Q amplifier sharing technique is presented for wireless receivers. To achieve high linearity even at 0.9-V supply, the clock signals to sampling switches are boosted over 0.9 V in conversion stages. The clock-boosting circuit for lifting these clocks is shared between I-ch ADC and Q-ch ADC, reducing the area penalty. Low supply voltage narrows the available output range of the operational amplifier. A pseudo-differential (PD) amplifier with two-gain-stage common-mode feedback (CMFB) is proposed in views of its wide output range and power efficiency. This ADC is fabricated in 90-nm CMOS technology. At 40 MS/s, the measured SNDR is 59.3 dB and the corresponding effective number of bits (ENOB) is 9.6. Until Nyquist frequency, the ENOB is kept over 9.3. The ADC dissipates 17.3 mW/ch, whose performances are suitable for ADCs for mobile wireless systems such as WLAN/WiMAX.

Placing a guard trace next to a signal line is the conventional technique for reducing the common-mode radiation from a printed circuit board. In this paper, the suppression of common-mode radiation from printed circuit boards having guard traces is estimated and evaluated using the imbalance difference model, which was proposed by the authors. To reduce common-mode radiation further, a procedure for designing a transmission line with guard traces is proposed. Guard traces connected to a return plane through vias are placed near a signal line and they decrease a current division factor (CDF). The CDF represents the degree of imbalance of a transmission line, and a common-mode electromotive force depends on the CDF. Thus, by calculating the CDF, we can estimate the reduction in common-mode radiation. It is reduced not only by placing guard traces, but also by narrowing the signal line to compensate for the variation in characteristic impedance due to the guard traces. Experimental results showed that the maximum reduction in common-mode radiation was about 14 dB achieved by placing guard traces on both sides of the signal line, and the calculated reduction agreed with the measured one within 1 dB. According to the CDF and characteristic impedance calculations, common-mode radiation can be reduced by about 25 dB while keeping the characteristic impedance constant by changing the gap between the signal line and the guard trace and by narrowing the width of the signal line.

Printed circuit boards (PCBs) driven by a connected feed cable are considered to be one of the main sources of the electromagnetic interference (EMI) from electronic devices. In this paper, a method for predicting the electromagnetic (EM) radiation from a PCB driven by a connected feed cable at up to gigahertz frequencies is proposed and demonstrated. The predictive model is based on the transmission line theory and current- and voltage-driven CM generation mechanisms with consideration of antenna impedance. Frequency responses of differential-mode (DM) and common-mode (CM) currents and far-electric field were investigated experimentally and with finite-difference time-domain (FDTD) modeling. First, the dominant component in total EM radiation from the PCB was identified by using the Source-Path-Antenna model. Although CM can dominate the total radiation at lower frequencies, DM is the dominant component above 3 GHz. Second, the method for predicting CM component at lower frequencies is proposed. And its validity was discussed by comparing FDTD calculated and measured results. Specifically, the relationship between the CM current and the terminating resistor was focused as important consequence for the prediction. Good agreement between the measured and predicted results shows the validity of the predicted results. The proposed model can predict CM current with sufficient accuracy, and also identify the primary coupling-mechanism of CM generation. Then far-electric field was predicted by using the proposed method, and it was demonstrated that outline of the frequency response of the undesired EM radiation from the PCB driven by the connected feed cable can be predicted with engineering accuracy (within 6 dB) up to 18 GHz. Finally, as example of application of equivalent circuit model to EMC design, effect of the width of the ground plane was predicted and discussed. The equivalent circuit model provides enough flexibility for different geometrical parameters and increases our ability to provide insights and design guidelines.

A guard trace placed near a signal line reduces common-mode radiation from a printed circuit board. The reduction effect is evaluated by the imbalance difference model, which was proposed by the authors, when the guard trace has exactly the same potential as the return plane. However, depending on interval of ground connection of the guard trace, the radiation can increase when the guard trace resonates. In this paper, the authors show that the increase of radiation is caused by the common mode, and extend the imbalance difference model to explain a mechanism of increase of common-mode radiation. Additionally, the effective via location of the guard trace is proposed to reduce the number of vias. The guard trace voltage due to the resonance excites the common mode at the interface where the cross-sectional structure of the transmission line changes since the common-mode excitation is expressed by the product of the voltage and the difference of current division factors. To suppress the common-mode excitation, the guard trace should be grounded at the point where the cross-sectional structure changes. As a result, the common-mode radiation decreases even when the guard trace resonates.

This paper describes 10-bit, 80-MSample/s pipelined A/D converters for wireless-communication terminals. To reduce power consumption, we employed the I/Q amplifier sharing technique [1] in which an amplifier is used for both I and Q channels. In addition, common-source, pseudo-differential (PD) amplifiers are used in all the conversion stages for further power reduction. Common-mode disturbances are removed by the proposed common-mode feedforward (CMFF) technique without using fully differential (FD) amplifiers. The converter was implemented in a 90-nm CMOS technology, and it consumes only 24 mW/ch from a 1.2-V power supply. The measured SNR and SNDR are 58.6 dB and 52.2 dB, respectively.

This paper describes a capacitive voltage probe (CVP) that can measure a common-mode voltage on a cable without touching its conductor. This CVP has two coaxial electrodes: the inner electrode works as a voltage pickup and the outer one shields the inner electrode. These electrodes separate into two parts for clamping to the cable. Using a high input impedance circuit, this probe measures the common-mode voltage by detecting the voltage difference between the two electrodes. The probe characteristics are evaluated by measuring its linearity and frequency response. The results show that this probe has a dynamic range of 100 dB and flat frequency response from 10 kHz to 30 MHz. Deviations in sensitivity due to the position of the clamped cable in the inner electrode and to differences in the cable radius are evaluated theoretically and experimentally. The results indicate that the influence of the cable position can be calibrated. Finally, measured data obtained using both an impedance stabilizing network (ISN) and a CVP are compared to confirm the validity of the CVP. The results show that data measured by the CVP closely agreed with that obtained by the ISN. Therefore, the CVP is useful for EMC measurements to evaluate common-mode disturbances.